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Thread: File I/O

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    Default File I/O

    Hello,
    I am new here so if my post is not within any guidelines i apologize i did search for this topic before i posted. I am a little confused on my current project and was hoping for some clarification. I am to write a program that asks the user to enter the name of the text file and then displays (StringTokenized) line, word, and char counts for the total output. The text file is one that i write as output to be stored behind the scenes. This program uses file I/O. My main difficulty at this point is that i understand how to have the output written to the .txt file in the computer (via a series of print statements) and i am able to access the file. I don't understand how the user would input the file? Would i have a class that does the output behind the scenes, and then the user input class to have the file accessed? Thank you.


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    Default Re: File I/O

    how the user would input the file
    Do you mean the contents of the file
    or the name of an existing file?

    See the Scanner class for an easy way to read input from a user from the console.

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    Default Re: File I/O

    I am given the contents to make the file (6 lines of words). I make the file using output. I see the scanner and input stuff i am just not understanding what exactly to do? I have to ask the user to enter the name of a file (which there going to be entering the name of the file which i already created. Then i have to access that file, and then parse the tokens from the input lines?

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    Default Re: File I/O

    You can also use the Scanner class to read the contents of the file.

    There are many sample programs on the forumthat use the Scanner class. Do a Search here.
    Also be sure to read the API doc for the Scanner class.
    Java Platform SE 6

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    Default Re: File I/O

    Thank you for that. Do i need to have both input and output inside my try block though? I do not understand where the output file is supposed to be implemented? Do i use the input and output statements inside the try block or do i just implement the input statement?

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    Default Re: File I/O

    It does not cause problems if you put extra statements inside of the try block.
    The one thing that can be a problem is the scope of any variables defined inside a try block. They won't be known outside of the enclosing {}s.
    Be sure to define all variables that you want to use at the same nesting level of {}s so that they are in scope where you try to use them.

    If you read the API doc for the methods you are using, it will say if the method can throw an exception and needs to be in try/catch blocks. The compiler will also tell you when you try to compile the code.

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    Default Re: File I/O

    When the assignment says "Write a program that asks the user to enter the name of a text file and then displays the counts", does that mean that i will have the question pop up in the output and create a scanner object to allow the user to enter a text file name?

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    Default Re: File I/O

    I assume that "asks the user" means you need to display a message and provide a way for the user to enter the filename that can be read into the program. The Scanner class has methods for reading input from a user into a variable.

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    Default Re: File I/O

    here is what i have so far. I am trying to figure out the I/O thing when it comes to user input in the program itself.
    Last edited by jan07; February 29th, 2012 at 04:24 PM.

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    Default Re: File I/O

    import java.io.*;
    import java.util.*;
     
    public class Project5
    {
        public static void main(String[] args) throws IOException
        {
            Scanner inputStream = null;
            PrintWriter outputStream = null;
            System.out.println("Please enter a file name");
            Scanner keyboard = new Scanner(System.in);
            String name = keyboard.nextLine();
            File file = new File(name);
            try
            {
     
            	inputStream = new Scanner(new FileInputStream(file));
                outputStream = new PrintWriter(new FileOutputStream("numbered.txt"));
     
            }
            catch(FileNotFoundException e)
            {
                System.out.println("Error");
                System.exit(0);
            }
     
            outputStream.println("Little miss Muffet,");
            outputStream.println("sat on a tuffet,");
            outputStream.println("eating her candy away.");
            outputStream.println("Along came a spider,");
            outputStream.println("who sat down beside her,");
            outputStream.println("and said \"Will you marry me?\"");
     
     
            int count = 0;
            String line = null;
            while(inputStream.hasNext())
            {
               line = inputStream.next();
               count ++;
     
            }
            outputStream.println("Word count:"+count);
            inputStream.close();
            outputStream.close();
     
     
     
        }
     
    }

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    Default Re: File I/O

    How did it go when you executed the code? What happened?

    In your catch block you should call the Event class's printStackTrace() method to show any exception.

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    Default Re: File I/O

    it asks me to enter the file i enter the file and that is all that happens. I don't believe it is accessing the actual file that i am trying to reference. I have not used printStackTrace() before i am not quite sure what it is? I guess at this point i am just trying to make sure i can access the file properly through user keyboard input and then next i will deal with parsing the file up?

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    Default Re: File I/O

    that is all that happens.
    Add some println statements to the code to show where it is executing and what the values of the variables are as they are set and changed. Their output will show you some of what the program is doing.

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    Default Re: File I/O

    so would i even need the outputStream statements in this program or do i need to just have it written to file once, and then use input statements to access it?

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    Default Re: File I/O

    would i even need the outputStream statements
    You don't need an OutputStream if you are not writing anything to a file.

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    Default Re: File I/O

    It gives me the little miss muffet etc... lines and the assignment says that it is the sample text file to be used as an input to my program, so i am uncertain if the i just create that file or if i have it as part of the program?

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    Default Re: File I/O

    i am uncertain if the i just create that file or if i have it as part of the program?
    Can you ask your instructor what the assignment is so you will know?

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    Default Re: File I/O

    No but i can write it out word for word?

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    Default Re: File I/O

    It all depends on what the assignment requires the program to do.
    You could create the file that is to be read by using an editor and then have the program read it.

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    Default Re: File I/O

    Write a program that asks the user to enter the name of a text file and then displays the line count, word(token) count and the character(non-delimeter) count in the file in a nice format. Use the StringTokenizer class in the java.util pacjkage to parse the tokens from the input lines. In addition to the whitespace characters, question mark(?), double quotes("), commas(,) and periods(.) should also be treated as delimeters and thus not to be counted as tokens or parts of tokens. Use the sample text file input5.txt as an input to your program.


    input5.txt
    Little miss Muffet,
    sat on a tuffet,
    eating her candy away.
    Along came a spider,
    who sat down beside her,
    and said "Will you marry me?"

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    Default Re: File I/O

    Create the file with an editor.

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